Drop compatibility with CMake < 2.4

Drop all behavior activated by setting CMAKE_BACKWARDS_COMPATIBILITY to
a value lower than 2.4, and generate an error when projects or the user
attempt to do so.  In the error suggest using a CMake 2.8.x release.

Teach cmake_minimum_required to warn about projects that do not require
at least CMake 2.4.  They are not supported by CMake >= 3.0.

Replace the documentation of CMAKE_BACKWARDS_COMPATIBILITY with a
reference to policy CMP0001.

17 files changed, 40 insertions, 10 deletions

diff --git a/Tests/Complex/CMakeLists.txt b/Tests/Complex/CMakeLists.txt
index 50dccbe..6711147 100644
--- a/Tests/Complex/CMakeLists.txt
+++ b/Tests/Complex/CMakeLists.txt
@@ -1,7 +1,7 @@
 #
 # A more complex test case
 #
-set(CMAKE_BACKWARDS_COMPATIBILITY 1.4)
+cmake_minimum_required(VERSION 2.4)
 project (Complex)
 
 # Try setting a new policy.  The IF test is for coverage.
diff --git a/Tests/Complex/Executable/CMakeLists.txt b/Tests/Complex/Executable/CMakeLists.txt
index 2613f27..bf23d4a 100644
--- a/Tests/Complex/Executable/CMakeLists.txt
+++ b/Tests/Complex/Executable/CMakeLists.txt
@@ -1,4 +1,3 @@
-cmake_minimum_required(VERSION 1.3)
 #
 # Create exe.
 #
diff --git a/Tests/Complex/Executable/complex.cxx b/Tests/Complex/Executable/complex.cxx
index e904f28..31442ba 100644
--- a/Tests/Complex/Executable/complex.cxx
+++ b/Tests/Complex/Executable/complex.cxx
@@ -838,13 +838,13 @@ int main()
 #endif
 #endif // defined(_WIN32) && !defined(__CYGWIN__)
 
-  if(strcmp(CMAKE_MINIMUM_REQUIRED_VERSION, "1.3") == 0)
+  if(strcmp(CMAKE_MINIMUM_REQUIRED_VERSION, "2.4") == 0)
     {
-    cmPassed("CMAKE_MINIMUM_REQUIRED_VERSION is set to 1.3");
+    cmPassed("CMAKE_MINIMUM_REQUIRED_VERSION is set to 2.4");
     }
   else
     {
-    cmFailed("CMAKE_MINIMUM_REQUIRED_VERSION is not set to the expected 1.3");
+    cmFailed("CMAKE_MINIMUM_REQUIRED_VERSION is not set to the expected 2.4");
     }
 
   // ----------------------------------------------------------------------
diff --git a/Tests/ComplexOneConfig/CMakeLists.txt b/Tests/ComplexOneConfig/CMakeLists.txt
index cbb4286..1abf45d 100644
--- a/Tests/ComplexOneConfig/CMakeLists.txt
+++ b/Tests/ComplexOneConfig/CMakeLists.txt
@@ -1,7 +1,7 @@
 #
 # A more complex test case
 #
-set(CMAKE_BACKWARDS_COMPATIBILITY 1.4)
+cmake_minimum_required(VERSION 2.4)
 project (Complex)
 
 # Try setting a new policy.  The IF test is for coverage.
diff --git a/Tests/ComplexOneConfig/Executable/CMakeLists.txt b/Tests/ComplexOneConfig/Executable/CMakeLists.txt
index 432dbf8..01f1005 100644
--- a/Tests/ComplexOneConfig/Executable/CMakeLists.txt
+++ b/Tests/ComplexOneConfig/Executable/CMakeLists.txt
@@ -1,4 +1,3 @@
-cmake_minimum_required(VERSION 1.3)
 #
 # Create exe.
 #
diff --git a/Tests/ComplexOneConfig/Executable/complex.cxx b/Tests/ComplexOneConfig/Executable/complex.cxx
index e904f28..31442ba 100644
--- a/Tests/ComplexOneConfig/Executable/complex.cxx
+++ b/Tests/ComplexOneConfig/Executable/complex.cxx
@@ -838,13 +838,13 @@ int main()
 #endif
 #endif // defined(_WIN32) && !defined(__CYGWIN__)
 
-  if(strcmp(CMAKE_MINIMUM_REQUIRED_VERSION, "1.3") == 0)
+  if(strcmp(CMAKE_MINIMUM_REQUIRED_VERSION, "2.4") == 0)
     {
-    cmPassed("CMAKE_MINIMUM_REQUIRED_VERSION is set to 1.3");
+    cmPassed("CMAKE_MINIMUM_REQUIRED_VERSION is set to 2.4");
     }
   else
     {
-    cmFailed("CMAKE_MINIMUM_REQUIRED_VERSION is not set to the expected 1.3");
+    cmFailed("CMAKE_MINIMUM_REQUIRED_VERSION is not set to the expected 2.4");
     }
 
   // ----------------------------------------------------------------------
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 8148cb6..e84aba2 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -93,6 +93,7 @@ add_RunCMake_test(Syntax)
 
 add_RunCMake_test(add_dependencies)
 add_RunCMake_test(build_command)
+add_RunCMake_test(cmake_minimum_required)
 add_RunCMake_test(find_package)
 add_RunCMake_test(get_filename_component)
 add_RunCMake_test(if)
diff --git a/Tests/RunCMake/cmake_minimum_required/Before24-stderr.txt b/Tests/RunCMake/cmake_minimum_required/Before24-stderr.txt
new file mode 100644
index 0000000..4a6f16d
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/Before24-stderr.txt
@@ -0,0 +1,5 @@
+CMake Warning \(dev\) at Before24.cmake:1 \(cmake_minimum_required\):
+  Compatibility with CMake < 2.4 is not supported by CMake >= 3.0.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/cmake_minimum_required/Before24.cmake b/Tests/RunCMake/cmake_minimum_required/Before24.cmake
new file mode 100644
index 0000000..c28fc8a
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/Before24.cmake
@@ -0,0 +1 @@
+cmake_minimum_required(VERSION 2.2)
diff --git a/Tests/RunCMake/cmake_minimum_required/CMakeLists.txt b/Tests/RunCMake/cmake_minimum_required/CMakeLists.txt
new file mode 100644
index 0000000..e8db6b0
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/CMakeLists.txt
@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 2.8)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/cmake_minimum_required/CompatBefore24-result.txt b/Tests/RunCMake/cmake_minimum_required/CompatBefore24-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/CompatBefore24-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_minimum_required/CompatBefore24-stderr.txt b/Tests/RunCMake/cmake_minimum_required/CompatBefore24-stderr.txt
new file mode 100644
index 0000000..a874466
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/CompatBefore24-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error in CMakeLists.txt:
+  You have set CMAKE_BACKWARDS_COMPATIBILITY to a CMake version less than
+  2.4.  This version of CMake only supports backwards compatibility with
+  CMake 2.4 or later.  For compatibility with older versions please use any
+  CMake 2.8.x release or lower.
diff --git a/Tests/RunCMake/cmake_minimum_required/CompatBefore24.cmake b/Tests/RunCMake/cmake_minimum_required/CompatBefore24.cmake
new file mode 100644
index 0000000..ca0cb1d
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/CompatBefore24.cmake
@@ -0,0 +1,2 @@
+cmake_minimum_required(VERSION 2.4)
+set(CMAKE_BACKWARDS_COMPATIBILITY 2.2)
diff --git a/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-result.txt b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-stderr.txt b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-stderr.txt
new file mode 100644
index 0000000..840211a
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24-stderr.txt
@@ -0,0 +1,6 @@
+CMake Error at PolicyBefore24.cmake:2 \(cmake_policy\):
+  Compatibility with CMake < 2.4 is not supported by CMake >= 3.0.  For
+  compatibility with older versions please use any CMake 2.8.x release or
+  lower.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/cmake_minimum_required/PolicyBefore24.cmake b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24.cmake
new file mode 100644
index 0000000..62d3836
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/PolicyBefore24.cmake
@@ -0,0 +1,2 @@
+cmake_minimum_required(VERSION 2.4)
+cmake_policy(VERSION 2.2)
diff --git a/Tests/RunCMake/cmake_minimum_required/RunCMakeTest.cmake b/Tests/RunCMake/cmake_minimum_required/RunCMakeTest.cmake
new file mode 100644
index 0000000..e4c65e3
--- /dev/null
+++ b/Tests/RunCMake/cmake_minimum_required/RunCMakeTest.cmake
@@ -0,0 +1,5 @@
+include(RunCMake)
+
+run_cmake(Before24)
+run_cmake(CompatBefore24)
+run_cmake(PolicyBefore24)